SylixOS 线程取消处理流程

Posted 2021-01-07

概述
取消一个线程要确保该线程能够释放其所持有的锁、分配的内存，使整个系统保持一致性。线程取消的途径有两种：异步取消和延时取消。

异步取消：被取消线程收到取消信号后，立即死亡。该线程缩持有的资源可能得不到释放，这是一种非安全的线程取消方式。

延时取消：系统默认取消方式，是一种比较安全的线程取消机制，被取消线程取消时，只是设置取消点(ptcbDel->TCB_bCancelRequest)为true，被取消线程继续运行，等到安全位置后进行取消操作。

取消点: 在使用延迟取消机制时，一个线程在可以被取消的地方定义取消点，当收到取消请求时，被取消的线程执行到取消点时退出，或者在一个取消点调用被阻塞时退出。

关键结构体
程序清单2.1 TCB结构体部分节选

typedef struct __lw_tcb {

...

??? LW_LIST_LINE????????? TCB_lineManage;????????? /? 内核管理用线表????????????? /

??? LW_LIST_RING????????? TCB_ringReady;?????????? /? 相同优先级就绪环??????????? /

???

??? LW_CLASS_WAKEUP_NODE? TCB_wunDelay;????? /? 等待节点??????????????????? /

#define TCB_ulDelay?????? TCB_wunDelay.WUN_ulCounter

...

#if (LW_CFG_EVENT_EN > 0) && (LW_CFG_MAX_EVENTS > 0)

??? LW_LIST_RING????????? TCB_ringEvent;????????? ???/? 事件等待队列表????????????? /

??? PLW_CLASS_EVENT?????? TCB_peventPtr;??????????? /? 等待事件指针????????????? ?/

??? PLW_LIST_RING??????? TCB_ppringPriorityQueue;????? /? 在 PRIORITY 队列位置???? */

??????????????????????????????????????????????? /? 由于删除线程时需要解等待链，/

?????????????????????????????????????????????? /? 这时需要确定队列位置??????? /

#endif

#if LW_CFG_COROUTINE_EN > 0

??? LW_CLASS_COROUTINE??? TCB_crcbOrigent;???????? /? 协程起源点????????????????? /

??? PLW_LIST_RING???????? TCB_pringCoroutineHeader;?? /? 协程首地址???????????????? /

#endif??????????????????????????????????????????? /? LW_CFG_COROUTINE_EN > 0???? /

...

??? volatile ULONG??????? TCB_ulCPUId;?????????? /? 如果正在运行, 表示运行 CPU? /

??? volatile BOOL???????? TCB_bIsCand;?????????? /? 是否在候选运行表中???????? ?/

#if LW_CFG_SMP_EN > 0

??? struct __lw_tcb????? TCB_ptcbWaitStatus;????????? /? 等待状态修改的目标线程????? */

??? PLW_LIST_LINE???????? TCB_plineStatusReqHeader;???? /? 等待修改本线程状态?????? /

??? LW_LIST_LINE????????? TCB_lineStatusPend;????????? /? 等待目标线程状态修改?? ????/

#endif?????????????????????????????????????????????? /? LW_CFG_SMP_EN????????????? /

...

??? PLW_EVENTSETNODE????? TCB_pesnPtr;????? /? 指向该线程等待????????????? /

...

#if LW_CFG_THREAD_CANCEL_EN > 0

??? BOOL????????????????? TCB_bCancelRequest;???? /? 取消请求??????????????????? /

??? INT?????????????????? TCB_iCancelState;???????? /? 取消状态??????????????????? /

??? INT?????????????????? TCB_iCancelType;????????? /? 取消类型??????????????????? /

#endif???????????????????????????????????????? /? LW_CFG_THREAD_CANCEL_EN???? /

...

#if LW_CFG_THREAD_DEL_EN > 0

??? struct __lw_tcb????? TCB_ptcbDeleteMe;?????? /? 要将本线程删除的 TCB??????? */

??? struct __lw_tcb????? TCB_ptcbDeleteWait;???????? /? 等待对方删除的 TCB????????? */

#endif???????????????????????????? ????????????????/? LW_CFG_THREAD_DEL_EN > 0??? /

??? UINT8???????????????? TCB_ucStackAutoAllocFlag;???? /? 堆栈是否有系统在堆中开辟?? /????????

??? PVOID???????????????? TCB_pvVProcessContext;?????? /? 进程上下文???????????????? /

...

} LW_CLASS_TCB;

程序清单2.2 等待队列

typedef union {

??? PLW_LIST_RING???????? WL_pringFifo;????????????????? /? 基于先入先出的等待队列?? /

??? PLW_LIST_RING???????? WL_pringPrio[__EVENT_Q_SIZE];? /? 基于优先级的等待队列?? /

} LW_UNION_WAITLIST;

typedef LW_UNION_WAITLIST *PLW_UNION_WAITLIST;

typedef struct {

??? LW_UNION_WAITLIST???? WQ_wlQ;??????????????? /? 等待队列??????????????????? /

??? UIN×××6??????????????? WQ_usNum;??????????????? /? 等待队列中的线程个数??????? /

} LW_CLASS_WAITQUEUE;

typedef LW_CLASS_WAITQUEUE *PLW_CLASS_WAITQUEUE;

程序清单2.3 事件集

typedef struct {???????????????????????????????????????????? /? 事件集??????????????????? /

??? LW_LIST_MONO???????? EVENTSET_monoResrcList;???? /? 空闲资源表?????????????? /

??? UINT8??????????????? EVENTSET_ucType;????????????? /? 类型????????????????????? /

??? PLW_LIST_LINE??????? EVENTSET_plineWaitList;??????? /? 指向第一个等待线程??????? /

??? ULONG??????????????? EVENTSET_ulEventSets;???????? /? 32 bit 事件位???????????? /

??? ULONG??????????????? EVENTSET_ulOption;?????????? /? 事件集选项??????????????? /

??? UIN×××6?????????????? EVENTSET_usIndex;???????????? /? 数组中的索引????????????? /

??? CHAR???????????????? EVENTSET_cEventSetName[LW_CFG_OBJECT_NAME_SIZE];

???????????????????????????????????????????????????????? /? 事件标志组名????????????? ?/

} LW_CLASS_EVENTSET;

typedef LW_CLASS_EVENTSET *PLW_CLASS_EVENTSET;

typedef struct {????????????????????????????????????????????? /? 事件集节点?????????????? /

??? LW_LIST_LINE???????? EVENTSETNODE_lineManage;???? /? 事件标志组管理表??????? /

???

??? PVOID???????? ???????EVENTSETNODE_ptcbMe;?????? /? 指向等待任务的TCB??????? /

??? PVOID??????????????? EVENTSETNODE_pesEventSet;?? /? 指向标志组??????????????? /

??? ULONG??????????????? EVENTSETNODE_ulEventSets;?? /? 标志组开始等待?????????? /

??? UINT8??????????????? EVENTSETNODE_ucWaitType;???? /? 等待类型???????????????? /

} LW_CLASS_EVENTSETNODE;

typedef LW_CLASS_EVENTSETNODE?? *PLW_CLASS_EVENTSETNODE;

typedef PLW_CLASS_EVENTSETNODE?? PLW_EVENTSETNODE;

流程
API_ThreadCancel函数流程：

? ? ? 图3.1 API_ThreadCancel函数

API_ThreadTestCancel函数流程：

图3.2 API_ThreadTestCancel函数

pthread_delete函数流程：

图3.3 pthread_delete函数

__threadDelete函数流程：

图3.4 __threadDelete函数